Just minutes later, she got tangled in a question about a part of her resume that is an enduring mystery.

In the 18 months before launching her second presidential bid, Clinton gave nearly 100 paid speeches at banks, trade associations, charitable groups and private corporations. The appearances netted her $21.7 million — and voters very little information about what she was telling top corporations as she prepared for her 2016 campaign.

What she said — or didn't say — to Wall Street banks in particular has become a significant problem for her presidential campaign, as she tries to counter the unexpected rise of Democratic rival Bernie Sanders. He's put her in awkward position of squaring her financial windfall with a frustrated electorate.

Asked in the debate — and not for the first time — about releasing transcripts of those speeches, she said: "I will look into it. I don't know the status, but I will certainly look into it." She added, "My view on this is, look at my record."

Clinton addressed a broad swath of industries, speaking to supermarket companies in Colorado, clinical pathologists in Illinois and travel agents in California, to name several. Many of the companies and trade organizations that she addressed are lobbying Congress over a variety of interests.

She typically delivered an address, then answered questions from a pre-vetted interviewer. Her standard fee was $225,000, though occasionally it could range up to $400,000.

Hillary Clinton cast the financial industry as an adversary in her presidential campaign — despite the money that industry has poured into her White House effort. Bernie Sanders once again mischaracterized the share of the wealth taken by the very richest Americans.

A look at some of the claims...

"That's what they offered," said Clinton, when asked this week whether her fees were too high.

Clinton defended her appearances Friday, saying she thought the speeches were "a good way to communicate" and answer questions about her experience as secretary of state.

"It was a useful exercise for me, because it also enabled me to think through, kind of, where I was in the assessment of what I would do next," Clinton told MSNBC.

Other than her fees, which her campaign disclosed in response to media inquiries, details about most of her closed speeches are nearly impossible to find. The Associated Press and other news organizations have asked repeatedly for transcripts, and did so again Friday after her promise to review the issue. Last month, she laughed and turned away when a reporter specifically asked for transcripts of her speeches to Goldman Sachs.

"I don't think voters are interested in the transcripts of her speeches," Joel Benenson, Clinton's pollster, told reporters Friday. But it was a voter who asked about her transcripts at a town-hall event on CNN on Wednesday.

AP's inquiries to the campaign about her appearances before several Wall Street banks went unanswered. Deutsche Bank, which paid Clinton $475,000 for addresses in New York and Washington, declined to comment, as did Goldman Sachs.

Although many of her remarks were given to large groups, they were frequently barred to media coverage and few recordings are available online. In many instances, Clinton's contract prohibited her comments from being broadcast, transcribed or "otherwise reproduced," according a copy of one such agreement with the University of Buffalo.

In a few cases, details trickled out through company blogs and trade publications.

At the time, and increasingly as the months wore on, she was considered a likely prospect to run for president, despite the fact she said little to tip her hand publicly on whether she would.

When she addressed the National Multifamily Housing Council in April 2013, she focused on foreign affairs, including the Arab Spring and North Korea, and domestic issues like the federal debt, and answered questions from the chairman.

She deflected questions about whether she was considering a presidential run.

"That is certainly a question I haven't been asked — in all of 12 minutes," she cracked, according to a post on the organization's website. "I'm just returning to civilian life and getting reacquainted with something called normal life."

That post has since been taken down.

A reporter from the real estate blog The Real Deal was at her October 2014 speech to the annual convention of a commercial real estate women's network in Miami Beach. Clinton focused on boosting the number of women in the field and achieving parity with men. "It's so important for women like us to get out of our comfort zones and be willing to fail," she said, according to the blog. "I've done that, too, on a very large stage."

Speaking to a private crowd of 10,000 real estate people in San Francisco in November 2013, Clinton "affirmed the role realty places in American culture," according to another blog post. Press was banned but participants at the conference, hosted by the National Association of Realtors, tweeted photos of her on stage.

Many organizations she addressed were reluctant to share details or even confirm her attendance, in part because contracts for those kinds of speakers typically prohibit sharing that information.

"I made speeches to lots of groups," Clinton said this week. "I told them what I thought. I answered questions."